Filamentous phage, such as fd used in this study, are thread-shaped bacterial viruses. Their outer coat is a tube formed by thousands equal copies of the major coat protein pVIII (Figure 1, left). We constructed libraries of random peptides fused to all pVIII domains (landscape libraries, Figure 1, right), and selected phages that act as probes specific for a panel of test antigens and biological threat agents. Because the viral carrier is infective, phage borne bio-selective probes can be cloned individually and propagated indefinitely without needs of their chemical synthesis or reconstructing. We demonstrated that biorecognition layers fabricated from phage-derived probes bind biological agents and, as a part of an analytical platform, generate detectable signals. As elements of field-use detectors, they are superior to antibodies, since they are inexpensive, highly specific and strong binders, resistant to high temperatures and environmental stresses.